Introduction.—Ti:Sapphire laser “dynasty” in ultrafast optics [1]}, [2]} has lasted three decades primarily because of the superb time resolution (down to 5 fs) [3]} and high pulse energy (up to 250 J). However, the short upper-state lifetime (3.2 \(\mu \) s) and the requirement of green pump result in low repetition rate and low average power, which are unpleasant in applications such as material processing and coincident measurement [4]}. Industrial grade Yb-doped lasers have received increasing attention as a scientific research tool in recent years. In addition to compactness and robustness, the gain media have sub-millisecond upper-state lifetime and can be directly pumped by diode to achieve high repetition rate (up to tens of MHz) and high average power (up to kilowatts). However, the relatively narrow gain bandwidth only supports sub-picosecond to picoseconds pulses, leaving the applications based on few-cycle pulses still the playground of Ti:Sapphire laser [5]}.
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